Respiratory

Interstitial Lung Disease

Interstitial lung disease (ILD) is a heterogeneous group of disorders causing inflammation and/or fibrosis of the lung parenchyma; diagnosis depends on exposure and connective-tissue assessment, HRCT, physiology and specialist multidisciplinary review, while treatment is cause-specific and progression-focused.

In a nutshell

ILD is a heterogeneous group of parenchymal disorders causing inflammation and/or fibrosis. Think progressive exertional breathlessness, dry cough, fine bibasal crackles and restrictive physiology with low gas transfer. Confirm the pattern with HRCT and ILD MDT review, identify exposures, drugs and connective-tissue disease, then use cause-specific treatment plus specialist antifibrotic and supportive pathways.

Classic presentation

Progressive exertional breathlessness and dry cough with fine bibasal inspiratory crackles, exertional desaturation and sometimes clubbing.

Key points

ILD is a pattern and disease family, not a diagnosis that automatically means idiopathic pulmonary fibrosis.
HRCT plus physiology and clinical context are central; a confident IPF diagnosis requires ILD-experienced MDT consensus.
Restriction and low gas transfer are typical, but spirometry may be normal or mixed early; exertional desaturation is clinically important.
Always ask about occupational/domestic exposures, drugs and connective-tissue symptoms before calling an ILD idiopathic.
NICE recommends nintedanib for IPF with FVC above 80% predicted and lists nintedanib or pirfenidone for FVC 50% to 80% predicted; these are specialist pathways.
Nintedanib is also a NICE option for chronic progressive fibrosing ILD in adults within its marketing authorisation.
Acute deterioration is an emergency differential: exclude infection, embolism, oedema, pneumothorax and drug toxicity before attributing it to ILD.
Supportive care begins at diagnosis: pulmonary rehabilitation, oxygen assessment, smoking cessation, comorbidity treatment, symptom control and palliative planning.

First-line investigation

HRCT thorax with full pulmonary function testing, gas transfer, exercise oxygen assessment and cause-directed history, examination and blood tests, followed by specialist ILD MDT review.

Management

Recognise and escalate deterioration

For new hypoxaemia, severe breathlessness, sepsis or respiratory failure, stabilise with ABCDE assessment and urgent senior respiratory/critical-care input while investigating infection, embolism, oedema, pneumothorax, drug toxicity and acute exacerbation.^1,2

Confirm the pattern and cause

Use HRCT, pulmonary function tests, exercise oxygen assessment, exposure/drug/connective-tissue review and targeted blood tests, then obtain ILD-experienced MDT consensus; biopsy is selective and management-dependent.^1,2

Support function from diagnosis

Offer pulmonary rehabilitation, smoking cessation, vaccination, comorbidity treatment, symptom control and assessment for ambulatory or long-term oxygen; involve the ILD nurse and palliative-care team when appropriate.^1,4,9

Use cause-specific and progression-focused treatment

Remove exposures or causative drugs and treat connective-tissue, inflammatory or infectious disease through the appropriate specialist pathway; use NICE antifibrotic options only for the relevant IPF or progressive-fibrosing phenotype and current eligibility criteria.^1,6,7,3,8,5

Measure trajectory and plan ahead

Review symptoms, FVC, gas transfer, exercise capacity, oxygen need, exacerbations and treatment toxicity; discuss prognosis, palliative care and transplant assessment early enough to remain useful.^1,9

Exam traps

A UIP pattern is not automatically IPF: exclude connective-tissue disease, exposure, drug and other causes.
ILD is usually restrictive, but normal or mixed spirometry does not exclude it.
A chest X-ray may suggest ILD but HRCT defines the pattern and distribution.
Do not use a memorised immunosuppression regimen or antifibrotic eligibility threshold without checking the subtype, current NICE guidance and specialist prescribing pathway.
A sudden deterioration in known ILD is not automatically an acute exacerbation; actively assess infection, pulmonary embolism, oedema, pneumothorax and drug toxicity.

Illustrations

Normal versus fibrotic alveolar-capillary membraneDiagram contrasting a normal thin alveolar-capillary membrane with a fibrotic thickened interstitium, showing impaired oxygen diffusion.PassFinals · original

High-resolution CT honeycombingCT chest image showing peripheral, bibasal reticular shadowing and honeycomb change in a usual interstitial pneumonia pattern.Yale Rosen from USA, Wikimedia Commons · CC-BY-SA-2.0

Restrictive versus obstructive physiologyDiagram comparing restrictive physiology, with reduced lung volumes and preserved FEV1/FVC, with obstructive physiology.PassFinals · original

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.